It's getting more common when needing to say 'OK' or 'Spot on' to have the index finger bent, so the top of the O is flat and it makes a sort of rabbit shape. It's a gesture used in diving too, to indicate that the diver is OK and can go again.

The one that annoys me most of all is the thumb and little finger extended, the others curled round into the palm and then the thumb put to the ear, to indicate a telephone call.... eeuuggghhhh!!!

LTS